Biofilms are protective slime secretions that form around bacteria, making antibiotics much less effective. The skin’s outer layer also provides an additional barrier to antibiotics, which protects biofilm coated bacteria that have set up home there.

Testing 12 different ionic liquids, Samir Mitragotri at the University of California and colleagues found that they could interrupt biofilm formation of two pathogens, Pseudomonas aeruginosa and Salmonella enterica. The ionic liquids also helped the antibiotics to bypass the skin’s outer layer to attack the bacteria. How they achieve this is, however, unknown. Most of the ionic liquids showed antimicrobial activity, but one in particular, choline geranate, holds promise as a new way of treating infected wounds.